The invention relates to headlamps for a vehicle, especially those equipped with a reflector of the elliptical type.
A headlamp of this kind conventionally comprises a light source, a reflector of the elliptical type, a first focus of which is situated in the vicinity of the source, a converging lens a focal plane of which passes close to a second focus of the reflector, and glazing for closing off the headlamp. In certain cases, the lens may consist of the glazing itself.
When such a headlamp has to generate a beam with a regulatory cut-off, such as a dipped beam or an anti-fog beam, it includes a mask or screen interposed between the light source and the lens, which shades the part of the light which otherwise would be propagated above this cut-off.
One difficulty of this type of headlamp lies in the alteration of the profile of the cut-off. Such an alteration is needed especially when a headlamp designed, for example, for driving on the right, has to form a cut-off light beam adapted for driving on the left. It may also be desirable to produce a universal headlamp, selectively capable of generating a dipped beam, an anti-fog beam or a beam without a cut-off.
Document EP 0 794 382, for example, describes a headlamp equipped with a movable screen having a vertical sliding motion so as, on demand, to form a beam with a cut-off, and being controlled by an actuator for that purpose.
However, the changes of position of the masks of this type of headlamp take place with beam transitions which are either dazzling for an oncoming vehicle or else momentarily generate a truncated beam, which is dangerous in both cases.
In other cases, such as with the headlamp of document U.S. Pat. No. 5,673,990 with a screen tilting towards the front, the transition is visually less comfortable since it generates a blurring of the cut-off and/or chromatic distortion.
In an attempt to alleviate these drawbacks, there was proposed, in the document EP 0 780 624, a headlamp with a screen mounted movably in rotation about an axis parallel to the principal axis of the headlamp. However, this headlamp does not give entire satisfaction.
One object of the invention is to provide a headlamp making it possible to generate one or more cut-off beams by means of a transition which is not dangerous and is visually comfortable.
With a view to achieving this object, a headlamp for a vehicle is provided according to the invention, including a framework and at least one shading screen movable mounted in rotation about a rotational axis with respect to the framework, in which the axis is inclined with respect to a principal axis of illumination of the headlamp.
Thus, the inclination of the axis entails a relatively gentle visual transition upon a change of beam. This movement of the screen does not generate any aberration. This transition is not dangerous. Moreover, the screen or the screens can be given relatively substantial dimensions without encountering problems of size in the headlamp.
The headlamp according to the invention may moreover exhibit at least one of the following characteristics:
it includes at least two screens;
it includes four screens;
it includes screens which are rigidly fixed mutually;
the or each screen has a profile of curved shape;
the rotational axis is a secant to the principal axis;
the rotational axis is a secant at a point situated to the front of the headlamp by reference to the screens;
the rotational axis extends substantially in a vertical plane;
it includes a rotational axis inclined upwards towards the front of the headlamp;
the rotational axis is slightly inclined with respect to the horizontal plane;
it includes several movable screens formed by different portions of the same support;
the screens are formed by different free end edges of the support;
it includes a support of generally conical shape;
the screen, or at least one of the screens, is able to define one of the beams from among the following group:
dipped beam for driving on the left;
dipped beam for driving on the right;
dipped beam for driving in wet weather;
dipped beam for motorway driving; and
main beam,
it further includes one screen rigidly fixed to the framework;
the fixed screen is able to interact with the movable screen or at least one of the movable screens so as to form one beam of the headlamp;
it includes a reflector in the shape of a rotationally symmetric ellipsoid.
Other characteristics and advantages of the invention will emerge further on reading the following description of a preferred embodiment, given by way of non-limiting example.